Red blood cells are red blood cells, and red blood cell is a common name. Erythrocytes are the most numerous type of blood cell in the body, with a normal number of 4-5.5 million/mL in adult males and 3.5-5 million/mL in adult females. erythrocytes have a normal shape of a disc with two concave sides and a diameter of about 7.5 μm, and the average volume of erythrocytes is between 80-100 fL. Erythrocytes have important physiological functions in the human body because they contain hemoglobin, which can be combined with oxygen and also with carbon dioxide and plays an important transport role in the body. After combining with oxygen, it can be transported to the body’s tissue cells for use by the body, and at the same time, the carbon dioxide produced by the metabolism of tissue cells is transported to the lungs and expelled from the body. Therefore, red blood cells are the most numerous blood cells in the blood and play an important role.